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Our thanks to the author and Conference Organisers, a Committee consisting of both University and Industry colleagues.

The full paper will appear in the Conference Proceedings ('Recent Advances in Animal Nutrition - 2007', edited by Phil Garnsworthy and Julian Wiseman) published by Nottingham University Press in the autumn of 2007 www.nup.com

Courtesy of the 41st Annual University of Nottingham Feed Conference www.nottingham.ac.uk/biosciences/ah/research/conferences.php




Selection of dairy cattle for milk yield has linked the endocrine and metabolic controls of nutrient balance and reproductive events in that reproduction is compromised during periods of nutrient shortage such as in early lactation.

Although the energy costs for ovulation, and establishment and maintenance of an early developing embryo are likely negligible compared with the energy needs for maintenance and lactation of the dam, the metabolic and endocrine cues associated with negative energy balance (NEB) impair resumption of ovulatory cycles, oocyte and embryo quality, and establishment and maintenance of pregnancy in dairy cattle.

The nutrition during late gestation and early lactation has a tremendous impact on health and subsequent reproductive performance of dairy cows. Prevalence of periparturient diseases is high in high-producing dairy cows and these disorders tend to have negative impacts on resumption of postpartum cyclicity and fertility.

Particular attention should be paid to diseases associated with energy and Ca metabolism in high-producing cows.

Inadequate energy intake after calving has a detrimental impact on reproductive performance of cows. Cows under severe NEB have reduced peripheral concentrations of glucose, insulin and insulin-like growth factor-I (IGF-I), reduced peak frequency of LH pulses, increased concentrations of growth hormone (GH), nonesterified fatty acids (NEFA) and β-OHbutyrate (BHBA), and impaired ovarian activity. Peripheral changes in metabolite concentrations are thought to influence granulosa cell function and oocyte quality.

Slow recovery of ovarian activity during the postpartum period is a major impediment to insemination of cows immediately after the end of the voluntary waiting period. Not only lack of ovarian cyclicity influences detection of estrus, but it also reduces conception rate, and increases the risk for pregnancy loss. Recent data indicate that cows with delayed postpartum ovulation are more likely to experience subclinical endometritis, which further reduces conception rates.

Extended postpartum anestrus is magnified by losses of body condition (BCS) during early lactation. Cows with greater losses of BCS are more likely to experience a delay in postpartum cyclicity, and both anestrus and low BCS negatively impact fertility. Resumption of ovulatory cycles associated with energy balance seems to be mediated by a rise in plasma insulin and IGF-I, which are linked to nutritional status.

Insulin seems to be an important metabolic signal re-coupling the GH-IGF axis in the first few weeks postpartum, thereby increasing blood concentrations of IGF-I and estradiol. Feeding diets that promote higher plasma glucose and insulin might improve the metabolic and endocrine status of cows, expedite resumption of postpartum cyclicity, and enhance fertility.

Exciting strategies have been developed to integrate nutritional and reproductive management.

Feeding supplemental lipid has proven effective in enhancing reproductive performance of lactating dairy cows. Oftentimes energy status is not affected by feeding lipid and the positive impacts on fertility seem to be the result of extra-caloric effects. More specifically, some fatty acids have the ability to modulate PGF2α secretion, enhance follicle development, luteal function, fertilization rate, embryo quality, and pregnancy maintenance in dairy cows.

Although lipid supplementation often improves reproduction, fertility responses to different types of fatty acids are not always consistent.

Minimizing the incidence of uterine problems and reducing the risk for subclinical and clinical ketosis are expected to improve overall cow health and reproduction. Inadequate prepartum feed intake and suppression of the immune system compromises uterine health and increases the risk for acute postpartum metritis, which reduces fertility. Proper cows management to allow adequate feeding behavior during late gestation and early lactation is expected to minimize immunosuppression and the risk for uterine diseases.

Choline is required for synthesis of lipoproteins for lipid transport. Supplementation with rumen-protected choline has consistently reduced the risk for subclinical and clinical ketosis in dairy cows, and improves milk yield, although effects on reproduction are less clear.



Author: Jose Eduardo P. Santos
Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, USA.

Author: Jose Eduardo P. Santos

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11/13/2007

Ricardas Gailevicius Slanciausko 1-3/lzukt Lithuania - Lithuania

Very good article. Answer Checked by Engormix.com